The present invention relates to a method for monitoring a pollutant conversion capacity of a catalytically coated, oxidizing exhaust gas after-treatment component in an exhaust gas system of an internal combustion engine as well as to an open- and closed-loop control device, a computer program and a computer program product according to the preamble of the respective coordinate claims. This type of monitoring is, for example, typically used with three-way catalytic converters.
Stricter laws in the area of diagnosis of emission related components by a vehicle's onboard diagnostics (OBD) require the monitoring of all components of the exhaust gas after-treatment systems for adherence to certain OBD limit values, which are for the most part stated as a multiple of the emission limit values. In order to achieve the exhaust gas limit values required by the government, complex exhaust gas after-treatment systems are employed.
SCR catalytic converters (selective catalytic reduction) are used among other things for the conversion of nitrogen oxides. A specific ratio of NO to NO2 in the exhaust gas is necessary for an optimal operation of the SCR catalytic converter. The NO2 proportion of the total NOx is frequently designated as the feed gas composition.
The NO2 proportion is as a rule considerably too low in the untreated emissions of the internal combustion engine. In order to provide a suitable NO2 concentration, an oxidation catalytic converter (DOC) is disposed in the exhaust gas after-treatment system upstream of the SCR catalytic converter. As an alternative, it is also possible for a particle filter (DPF), which is correspondingly catalytically coated, to be provided in order to oxidize NO to NO2. An increased NO2 concentration in the exhaust gas also promotes the regeneration of the particle filter by oxygen from NO2 molecules being consumed for the oxidation of the carbon of the embedded soot particles. A lower flow resistance and a longer loading phase are achieved by reducing the particle loading of the particle filter. Both have a positive effect on emissions.
Because the operability of the exhaust gas after-treatment components is important for the adherence to emission limit values, lawmakers have stipulated that the operation of said components is to be monitored over the service life of the motor vehicles. For example, the monitoring of the coating of the oxidation catalytic converter and the particle filter is required.
There is currently not a method known, which monitors the catalytically coated exhaust gas components for their capacity to convert NO to NO2.